Leap years will have one more day than normal years, which is February 29 (Illustration: Pinterest).
Normally, each Gregorian year has 365 days, but a leap year has 366 days. There is a leap year every 4 years. Other calendars such as the Lunar calendar, the Hebrew calendar, and the Islamic calendar also have leap years, but they do not follow the rule of every 4 years. Some calendars also have leap days or leap months.
In addition to leap years and leap days, the Gregorian calendar also has leap seconds, which are occasional extra seconds added to certain years. The last leap seconds were added in 2012, 2015, and 2016. However, the International Bureau of Weights and Measures (IBWM), which is responsible for measuring time globally, will abolish leap seconds from 2035 onwards.
Why do we need leap years?
On the surface, adding an extra period to a year may sound like a silly idea, but leap years are actually very important.
We have leap years because a normal Gregorian year is slightly shorter than a solar year - the time it takes for the Earth to complete one revolution around the Sun. A normal Gregorian year is exactly 365 days long, but a solar year is about 365.24 days long, or 365 days, 5 hours, 48 minutes and 56 seconds.
If we did not take this difference into account, then with each passing year the gap between the beginning of a calendar year and a solar year would increase by 5 hours 48 minutes and 56 seconds. For example, if we did not include leap years, then after about 700 years, summer in the Northern Hemisphere would begin in December instead of June.
The extra day in a leap year solves that problem. However, this adjustment system is not completely accurate. Every four years, we gain about 44 minutes, which is equivalent to one extra day every 129 years.
To solve this problem, every hundred years we skip a leap year, except for years divisible by 400 like 1600 and 2000. But even then, there is still a small difference between the Gregorian year and the Solar year, so IBWM tried adding leap seconds.
Since when did we start having leap years?
The idea of introducing a leap year into the calendar dates back to 45 BC, when the ancient Roman Emperor Julius Caesar introduced the Julian calendar, which has been in use since 46 BC. The Julian calendar has 445 days in a year divided into 15 months and also has a leap year every four years, synchronized with the seasons on Earth.
For many centuries, the Julian calendar was used normally, but by the mid-16th century, astronomers noticed that the seasons began about 10 days earlier than important holidays, such as Easter, and were no longer compatible with seasonal transitions such as the spring equinox or the vernal equinox.
To correct this, Pope Gregory XIII promulgated the Gregorian calendar, which is the Gregorian calendar we use today, in 1582. The Gregorian calendar is essentially the same as the Julian calendar but removes the leap year every 100 years as explained above.
For centuries, only Catholic countries such as Italy and Spain used the Gregorian calendar, but Protestant countries such as England eventually switched to it in 1752.
Because of the large differences between calendars, when these countries switched to the Gregorian calendar, they had to skip many days of their year to synchronize with other countries. For example, when Britain changed its calendar in 1752, September 2 was followed by September 14, skipping the days from September 3 to September 13.
At some point in the distant future, it is possible that the Gregorian calendar will be rethought because it will no longer be synchronized with the solar year, but that will be thousands of years away.
According to LiveScience
Source
Comment (0)